Introduction

The Economist’s Big Mac Index was invented in 1986 as a lighthearted guide to whether currencies are at their “correct” level. It is based on the theory of purchasing-power parity (PPP), the notion that in the long run exchange rates should move towards the rate that would equalise the prices of an identical basket of goods and services (in this case, a burger) in any two countries.

Burgernomics was never intended as a precise gauge of currency misalignment, merely a tool to make exchange-rate theory more digestible. Yet the Big Mac index has become a global standard, included in several economic textbooks and the subject of dozens of academic studies.

In this project we will take a look at how the Big Mac index evolved in the last 20 years and draw some insights from the last edition, published in January 2022.

The Economist has made the data for the index (along with the scripts used for the calculations) available in their repository in GitHub. A list with the continent of each country that appears in the index will be added the allow further analysis.

Data summary
Name	df
Number of rows	1577
Number of columns	20
_______________________
Column type frequency:
character	4
Date	1
numeric	15
________________________
Group variables	None

Variable type: character

skim_variable	complete_rate	min	max	n_unique
iso_a3	1	3	3	57
currency_code	1	3	3	58
name	1	3	20	58
continent	1	4	7	4

Variable type: Date

skim_variable	n_missing	complete_rate	min	max	median	n_unique
date	0	1	2000-04-01	2022-01-01	2014-07-01	36

Variable type: numeric

skim_variable	n_missing	complete_rate	mean	sd	p0	p25	p50	p75	p100	hist
local_price	0	1.00	19347.81	437615.11	1.05	7.63	27.49	130.00	16020000.00	▇▁▁▁▁
dollar_ex	0	1.00	5781.14	111753.56	0.30	3.07	7.76	51.00	3613989.07	▇▁▁▁▁
dollar_price	0	1.00	3.32	1.29	0.64	2.38	3.13	4.05	9.08	▃▇▃▁▁
USD_raw	0	1.00	-0.24	0.30	-0.87	-0.45	-0.30	-0.09	1.27	▃▇▂▁▁
EUR_raw	0	1.00	-0.23	0.27	-0.83	-0.44	-0.28	-0.07	0.87	▂▇▃▁▁
GBP_raw	0	1.00	-0.18	0.30	-0.85	-0.40	-0.23	0.00	1.14	▂▇▃▁▁
JPY_raw	0	1.00	0.04	0.39	-0.79	-0.25	0.00	0.24	2.16	▅▇▂▁▁
CNY_raw	0	1.00	0.44	0.63	-0.76	0.01	0.29	0.77	4.39	▇▇▁▁▁
GDP_dollar	710	0.55	25333.39	22576.39	1049.75	7114.33	14591.33	41277.48	100578.97	▇▂▂▁▁
adj_price	710	0.55	3.73	0.95	2.33	3.00	3.36	4.43	7.43	▇▃▃▁▁
USD_adjusted	710	0.55	-0.03	0.25	-0.58	-0.19	-0.03	0.09	1.49	▃▇▁▁▁
EUR_adjusted	710	0.55	-0.10	0.21	-0.58	-0.23	-0.10	0.01	0.82	▂▇▅▁▁
GBP_adjusted	710	0.55	0.00	0.24	-0.59	-0.15	0.00	0.14	1.29	▂▇▂▁▁
JPY_adjusted	710	0.55	0.23	0.30	-0.46	0.02	0.21	0.40	1.62	▂▇▃▁▁
CNY_adjusted	710	0.55	0.01	0.25	-0.55	-0.14	0.00	0.13	1.41	▃▇▂▁▁

The table above shows that the GDP and adjusted columns have missing values. This is because the adjusted index (based on the GDP per capita) was introduced in July 2011 and has a reduced number of countries, while the full index sometimes adds or removes countries.

The index is calculated over 5 ‘base’ currencies, but to keep it simple we will only analyze the one based on the US dollar (which is also the most representative), dropping the other ones. Country and currency codes will be also dropped.

Burgernomics across time

Since April 2000, there have been 36 editions of the index. While it was usually updated at the middle of each year (with some exceptions in 2006, 2007 and 2010), from 2012 it is updated in both January and July.

As it was previously said, The Economist sometimes adds or removes countries for the index. But how many haven’t always been part of the index? And which ones stayed on the least?

The countries that appeared the least are from the Middle East, Central America and Eastern Europe. They all were part of the index for 8 editions. Coincidence or not, they all have developing economies.

This leads us to another question: How is the trend? Does the overall number of countries included in the index change over time or there is always the same number that comes and goes?

We can see that there is a pattern to increase the number of countries in the index. In the last twenty years has gone from 28 to 57 countries, doubling its size.

Now, what has happened with the price of the Big Mac in the US, used as a base for all the other numbers to compare? As a reference, the American Consumer Price Index in the same period has increased a 66.7%.

Going from $2.51 to $5.65 the Big Mac has more than doubled its price in the US (a 131.4% increase to be precise), way more than the increase of the Consumer Price Index, which makes us question the reliability of the last one. Notice also that the price stayed stable in the years that followed financial crisis (the burst of the .com bubble in 2000, the subprime mortgages in 2008 and the COVID pandemic in 2020).

What happened with the price in the other countries? We made a ranking with the variations in their local currencies to get an idea.

The ranking shows us that the prices have increased in all the countries, altough in very different measures. While in countries like Israel, Switzerland and Taiwan they increased less than 20%, in Argentina the variation was of 15100%, which means that today you need 151 times the money you needed in 2000 to buy a Big Mac!

Having an idea about how the index evolved over time, we will next take a look at the last edition.

Burgernomics in 2022

First, we will rank the countries by the price in US dollars of the Big Mac, to see if there are any patterns.

There is a big difference between the top and the bottom of the ranking. A Big Mac in Switzerland costs up to 3.2 times more than in South Africa. We see that all the countries in the top of the list (except for Venezuela) are countries with a high GDP per capita, while the ones in the bottom have a low GDP.

To check if there is a correlation between the GDP per capita and the price of the Big Mac we are going to use a scatter plot.

There is a clear correlation between the two variables. This makes sense, you would expect average burger prices to be cheaper in poor countries than in rich ones because costs such as rent and worker’s wages are lower. To address this issue The Economist created an adjusted index, by using a linear regression of GDP vs Big Mac Price.

We will compare both versions to see how the correction affects the ranking.

There clearly is a difference when adjusting the index to GDP.

Bonus track: currency volatility

While the main objective of the Big Mac Index is to determine whether a country’s currency is too cheap or too expensive, the data can be used to draw alternative insights. For example, the volatility of a country’s exchange rate.

What is the relevance of this indicator? Let’s put it this way: Foreign investors inevitably seek out stable countries with strong economic performance in which to invest their capital. A country with such positive attributes will draw investment funds away from other countries perceived to have more political and economic risk.

By analyzing the standard deviation of each country’s adjusted index along time we can determine how stable are their exchange rates.

While all the countries had variations in their index (except the US, because we are using the USD adjusted index), only 4 of them really stood out with a standard deviation way above average (0.11). They were Argentina, Turkey, Colombia and Brazil. The common denominator is that they all are developing economies (and 3 of them are from South America). We will plot the evolution of each country’s index in order to see if they have similar trends.

The index for the South American countries have a similar trend: They were quite overvalued at the beginning of the decade, started decreasing until 2016, then increased until 2018 and fell again (although Argentina’s index has been increasing since 2019). In the same period, Turkey’s currency has been steadily depreciating.